Potential Functions for Internal Rotation about the C_(sp)~2-O Bond and Intramolecular Interactions in p-RC_6H_4OCH_3 Compounds

摘要

Potential functions for internal rotation about the C_(sp)~2-O bond in p-RC_6H_4OCH_3 compounds (R=NH_2,OCH_3,CH_3,H,F,Cl,CN,NO_2) were determined by nonempirical quantum-chemical calculations in the HF/6-31G~* and MP2/6-31G~* approximations with account taken of correlation energy for all electrons.The molecular conformation is planar.The height of the rotation barrier changes,depending on the electronic effect of para-substituent.Electron-donor substituents reduce while electron-acceptor substituents enhance the stability of the planar conformation.Using the natural bond orbital (NBO) approach,the nature of lone electron pairs on the methoxy oxygen atom was analyzed,and the energies for their resonance interaction with the antibonding aromatic pi~* orbitals were determined.The effect of para-substituent on the electron density distribution over the methoxy group and on the Koopmans first ionization potentials was estimated.Geometric parameters of the molecules under study are given.